PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative QCD )
There are 128 abstracts for this session.
61. Recent progress in NNLO QCD
We review some recent progress in next-to-next-to-leading order processes
in QCD, especially in connection with jet physics.
Authors:Zvi Bern, Lance Dixon and David Kosower
Proposed speaker: Zvi Bern
Contact person:Zvi Bern (UCLA), bern@physics.ucla.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/0001001, hep-ph/9903516
Notes:My talk would be more general than the above two papers.
79. Complete Renormalization Group Improvement- Avoiding Scale Dependence
in QCD Predictions
We show that all dependence on factorization and renormalization scales
is removed provided that all the ultra-violet logarithms involving the
physical energy scale ,Q, are completely resummed. In standard RG-improvement
the renormalization and factorization scales are taken proportional to
Q, if they are rather held independent of Q one is forced to identify and
resum to all-orders the ultra-violet logs, and all unphysical scales cancel.
A simple and direct method of extracting QCD lambda from experimental data
is advocated, and the approach is applied to the analysis of e+e- data
on jet observables over a wide range of energies, and fits are made to
determine the likely size of uncalculated higher-order corrections, and
possible power corrections.
Authors:C.J. Maxwell and A. Mirjalili
Proposed speaker: C.J. Maxwell
Contact person:Christopher J. Maxwell (University of Durham),
c.j.maxwell@durham.ac.uk
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/0002204 To be published in Nuclear
Physics B
Notes:The data analysis is in preparation in collaboration with
S.J. Burby and E.W.N. Glover
91. Uncertainties of Parton Distribution Functions and Their Implications
on Physics Predictions
We describe preliminary results from an effort to quantify the uncertainties
in parton distribution functions and the resulting uncertainties in predicted
physical quantities. Constraints due to the full data sets of the CTEQ
global analysis are used in this study. Two complementary approaches, based
on the Hessian and the Lagrange multiplier method respectively, are outlined.
We discuss issues on obtaining meaningful uncertainty estimates that include
the effect of correlated experimental systematic uncertainties. Implications
on W/Z and Higgs production at the Tevatron and LHC are given as examples.
Authors:R. Brock, D. Casey, J. Huston, J. Kalk, J. Pumplin, D.
Stump, W.K. Tung
Proposed speaker: Wu-Ki Tung
Contact person:Wu-Ki Tung (Michigan State University), Tung@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
103. Leading particle production in light flavour jets
The energy distribution and type of particle with the highest momentum
in quark jets are determined for each of the five quark flavours, with
minimal model assumptions. The analysis is based on hadronic Z0 decays
in the OPAL detector at LEP. We use our results to study the hadronisation
mechanism in light flavour jets and compare the data to the QCD models
JETSET and HERWIG. Within the JETSET model we also directly determine the
suppression of strange quarks to be 0.422 +- 0.049 +- 0.059 by comparing
the production of charged and neutral kaons in strange and non-strange
light quark events. Finally we study the features of baryon production.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-164, submitted to Eur. Phys. J.
C = http://opal.web.cern.ch/Opal/pubs/paper/html/pr296.html
Notes:Also Parallel session 2, Soft Processes; and Plenary session
12, Soft Processes
105. Charged multiplicities in Z decays into u, d and s quarks
About 4.4 million hadronic Z0 decays in the OPAL detector at LEP1 are used
to determine the mean charged particle multiplicities for the three light
quark flavours and to probe the flavour independence of the strong interaction.
Rates of charged particles are measured as: 17.77 +- 0.52 (+0.86,-1.20)
in uubar events, 21.44 +- 0.69 (+1.46,-1.17) in ddbar events and 20.02
+- 0.14 (+0.39,-0.37) in ssbar events (systematic errors are in parentheses).
With a prediction of the next-to-leading-log approximation of QCD these
numbers can be translated into flavour dependent values of alpha_s which
are consistent with the expectation of flavour independence of the strong
interaction.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: OPAL PN396 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn396.html
Notes:
113. QCD studies with e+e- annihilation data at 172-189 GeV
We have studied hadronic events from e+e- annihilation data at centre-of-mass
energies of 172, 183 and 189~GeV. We present distributions of event shape
variables, charged particle multiplicity and momentum, measured separately
in the three data samples. From these we extract measurements of the strong
coupling strength, the mean charged particle multiplicity, and the peak
position in the ln(1/x) distribution. In general the data are described
well by analytic QCD calculations and Monte Carlo models.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-178, submitted to Eur. Phys. J.
C > =http://opal.web.cern.ch/Opal/pubs/paper/html/pr303.html
Notes:4/13/00 TY- Fixed supporting papers, based on E-mail from
David dated 4/13.
114. QCD Analyses and Determinations of the Strong Coupling Strength in
e+e- Annihilations at Energies between 35 and 189 GeV
We employ data taken by the JADE and OPAL experiments for a QCD study in
hadronic e+e- annihilations at c.m. energies ranging from 35 GeV through
189 GeV. The observables are obtained using the JADE, Durham, Cambridge
and cone jet finders, and are compared with the predictions of QCD and
Monte Carlo models. The strong coupling strength is determined at each
energy by fits of fixed order and matched NLLA predictions to the data.
We obtain 0.1187+-0.0034(stat.)+-0.0019(syst). The strong coupling is also
obtained, at lower precision, from second order fits of the c.m. energy
evolution of some of the observabless.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-175, submitted to Eur. Phys. J.
C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr299.html
Notes:
115. Test of the Flavour Independence of alpha_s using Next-to-leading
Order Calculations for Heavy Quarks
We present a test of the flavour independence of the strong coupling constant
for charm and bottom quarks with respect to light (uds) quarks. Five observables
related to global event shapes were used to measure alpha_s in three flavour
tagged samples (uds, c and b). The event shape distributions were fitted
by second order calculations of jet production taking into account mass
effects for the c and b quarks. We find the ratio of alpha_s from c events
to uds events to be 0.997+-0.038(stat.)+-0.030(syst.)+-0.012(theory). The
corresponding quantity between b and uds events is 0.993+-0.008(stat.)+-0.006(syst.)+-0.011(theory).
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-045, Eur. Phys. J. C11 (1999) 643-659
=http://opal.web.cern.ch/Opal/pubs/paper/html/pr276.html
Notes:
116. Experimental Properties of Gluon and Quark Jets from a Point Source
Gluon jets are identified in Z$^0$ decays as the particles in a hemisphere
opposite to two tagged quark jets, corresponding to the definition of gluon
jets in calculations. Quark jets are selected as the particles in hemispheres
of tagged light quark (uds) events. For soft particles at large transverse
momentum, the charged particle multiplicity ratio of gluon to quark jets
is 2.29+-0.09(stat.)+-0.15(syst.), in agreement with the QCD prediction
of about 2.25. Our gluon jet data allow a sensitive test of color reconnection.
We test the model of color reconnection in the Ariadne Monte Carlo and
find it to be disfavoured.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-028, Eur. Phys. J. C11 (1999) 217-238
=http://opal.web.cern.ch/Opal/pubs/paper/html/pr273.html
Notes:
130. Combined recoil and threshold resummation for hard scattering cross
sections.
The radiation of soft gluons by hard scattering processes in near-elastics
kinematics accounts for large higher order enhancements to the partonic
cross section, but can also significantly influence transverse momentum
distributions via its recoil effects. We discuss how one may resum both
classes of higher order corrections consistently to next-to-leading logarithmic
accuracy, based on a generalized refactorization of the partonic cross
section near threshold. Results of numerical studies for prompt photon
production and Drell-Yan will be presented.
Authors:Eric Laenen, George Sterman, Werner Vogelsang
Proposed speaker: Eric Laenen
Contact person:Eric Laenen (NIKHEF), Eric.Laenen@nikhef.nl
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: HIGHER ORDER QCD CORRECTIONS IN PROMPT PHOTON
PRODUCTION. By Eric Laenen (NIKHEF, Amsterdam), George Sterman, Werner
Vogelsang (SUNY, Stony Brook). YITP-99-69, Feb 2000. 9pp. e-Print Archive:
hep-ph/0002078
Notes:
142. A measurement of the b-quark mass from hadronic Z decays
The three-jet rate as well as moments of event shape variables are measured
in hadronic Z decays from data taken with the ALEPH detector at LEP1, and
the ratio of the results found in b-tagged events and in the inclusive
sample is computed. Taking the three-jet rate, which is the optimal variable
with respect to the size of the hadronization corrections, a next-to-leading
order prediction including mass effects is fitted to the measured ratio
and thus the mass of the b-quark is determined.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
161. Inclusive Production of pi0,eta,eta'(958), K0S and Lambda in Two-
and Three-Jet Events from Hadronic Z Decays
The production rates and the inclusive cross sections of the isovector
meson pi0, the isoscalar mesons eta and eta'(958), the strange meson K0S
and the Lambda baryon have been measured as functions of scaled energy
in hadronic events, two-jet events and each jet of three-jet events from
hadronic Z decays and compared to Monte Carlo models. The JETSET modelling
of the gluon fragmentation into isoscalar mesons is found to be in agreement
with the experimental results. HERWIG fails to describe the K0S spectra
in gluon-enriched jets and the Lambda spectra in quark jets.
Authors:ALEPH Collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
162. Measurement of the Strong Coupling constant from 4-jet hadronic Z
decays
Data from e+e- annihilation into hadrons, taken with the ALEPH detector
at the Z pole, are analyzed. The 4-jet rate is studied as a function of
the resolution parameter and compared to next-to-leading order calculations
combined with a resummation of large logarithms. With this method, a first
measurement of the strong coupling constant alpha_s(M_Z) from 4-jet observables
is performed, showing good agreement with previous measurements.
Authors:ALEPH Collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
163. Inclusive Production of the omega(782) Vector Mesons in Hadronic Z
Decays
The inclusive production of the omega(782) vector meson in hadronic Z decays
is measured and compared to model predictions. The analysis is based on
4 million hadronic Z decays recorded by the ALEPH detector between 1991
and 1995. Decays of the omega -> pi+pi-pi0 are reconstructed for x_p >
0.05. In addition the branching ratio for omega -> mu+mu- is investigated.
Authors:ALEPH Collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
164. QCD Measurements in e+e- Annihilations at Centre-of-Mass Energies
between 192 and 202 GeV
Properties of hadronic events produced at LEP at centre-of-mass energies
between 192 and 202 GeV are studied and compared with QCD predictions.
Distributions of event-shape observables, jet rates and multiplicities
are presented and compared to the predictions of several Monte Carlo models
and analytic QCD calculations. From a fit of O(alpha_s^2)+NLLA QCD calculations
to distributions of event-shape variables, alpha_s has been determined
at those energies.
Authors:ALEPH Collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
173. Measurement of the effective b quark fragmentation function at the
Z peak
A model-independent study of the fragmentation of b quarks into B mesons
is presented using the full LEP 1 statistics. A semi-exclusive reconstruction
of B->D(*)l nu decays is performed, by combining the lepton candidates
with fully reconstructed D(*) mesons, while the neutrino energy is estimated
from the missing energy of the event. The result is also compared with
a number of different fragmentation models.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla (CERN), Fabrizio.Palla@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
250. pi0, eta, K0 and charged particle multiplicities in quark and gluon
jets
We compared the multiplicities of charged particles, pi0, eta and K0 in
quark and gluon jets. The comparisons were performed for distributions
unfolded to 100% pure gluon and quark jets, at an effective scale which
accounts for topological dependence of the three-jet environment. The ratio
of particle multiplicity in gluon jets to quark jets was found to be independent
of particle species, consistent with the QCD prediction. In particular,
we do not observe an enhancement in the eta production rate in gluon jets
beyond that found for the other types of particles.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: To be submitted to the conference and listed
on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
251. A simultaneous measurement of the strong coupling strength and the
QCD colour charges
We performed a simultaneous measurement of the strong coupling strength
alpha_s and the colour factors of the underlying gauge group of strong
interactions, CF and CA. The measurement was based on fitting next-to-leading-order
perturbative predictions to measured angular correlations of four-jet events,
in combination with multi-jet related variables. Our results are in agreement
with SU(3) expectations for CF and CA and with the world average value
of alpha_s.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: To be submitted to the conference and listed
on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
252. QCD studies with e+e- annihilation data at the highest LEP-2 energies
We have studied hadronic events from e+e- annihilation data at the highest
available centre-of-mass energies. We present distributions of event shape
variables, charged particle multiplicity and momentum. From these we extract
measurements of the strong coupling strength, the mean charged particle
multiplicity, and the peak position in the ln(1/x) distribution. In general
the data are described well by analytic QCD calculations and Monte Carlo
models.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: To be submitted to the conference and listed
on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
255. The Q^2 Dependence of the Di-Jet Cross Section in Photon-Photon Collisions
at LEP
Di-jet production is studied in collisions of quasi-real and virtual photons
at e+e- centre-of-mass energies from 198 to 200 GeV. The jets are reconstructed
using a cluster jet finding algorithm. The inclusive two-jet cross-section
is measured as a function of the transverse energy and the pseudorapidity
of the jets and compared to NLO perturbative QCD calculations and to the
prediction of Monte Carlo generators using different LO parametrisations
of the parton distributions of the photon.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: To be submitted to the conference and listed
on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to Parallel session 2, two-photon and
Plenary session 12, two photon
256. Measurement of the virtual photon structure function in Photon-Photon
Collisions at LEP
The virtual photon structure function is extracted from a measurement of
the cross section for the process e+e- -> e+e- gamma*gamma* -> e+e-X, where
X denotes the hadronic final state, using the OPAL detector based on data
from the 1998 LEP run. The scattered electrons have been tagged in the
OPAL luminometers. The upgrade of four calorimeter modules in the very
forward region at OPAL (z=7.8m) allows to study the virtual structure of
the photon for 0.1 < P^2 < 1.0 GeV^2. The results are compared to
Monte Carlo models using different descriptions of the P^2 suppression
of the photon.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: To be submitted to the conference and listed
on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to Parallel session 2, two-photon and
Plenary session 12, two photon
280. Towards NNLO QCD calculations: the IR behaviour of QCD amplitudes
at O(\as^2)
I discuss recent results on the infrared behaviour of tree-level and one-loop
QCD amplitudes at O(\alpha_S^2) which will be relevant to extend QCD predictions
to NNLO
Authors:Stefano Catani & Massimiliano Grazzini
Proposed speaker: Massimiliano Grazzini
Contact person:Massimiliano Grazzini (ETH),
grazzini@itp.phys.ethz.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: S.Catani and M.Grazzini, Nucl. Phys. B570
(2000) 287 and preprint in preparation
Notes:
305. Does Efficiency of Multiple Hadron Production Depend on a Hard Scale?
The average multiplicity of charged hadrons in the current fragmentation
region of both the c.m.s. and the Breit frame of deep inelastic scattering
is calculated and compared with the H1 and ZEUS data. The results are in
agreement with Yang's hypothesis that at fixed energy the efficiency of
hard collisions increases at larger momentum transfer.
Authors:Alexandre Kisselev and Vladimir Petrov
Proposed speaker: Alexandre Kisselev
Contact person:Alexandre Kisselev (Institute for High Energy
Physics (IHEP)), kisselev@mx.ihep.su
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
311. MULTIPLICITY DISTRIBUTIONS OF QUARK AND GLUON JETS IN QCD
The solution of the equations for the generating functions of multiplicity
distributions of quark and gluon jets in higher order perturbative QCD
is obtained. The non-perturbative effects are discussed as well. The results
are compared to recent experimental data on mean multiplicities, their
ratio and its slope, higher moments of the distributions.
Authors:I.M. DREMIN
Proposed speaker: I.M. DREMIN
Contact person:Igor M Dremin (Lebedev Physical Institute), dremin@lpi.ru
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
322. Neutrino DIS and the extraction of the strange sea density
We performed a new global analysis of DIS data with an enlarged neutrino
and antineutrino data set. Special emphasis is given to the strange sector.
For the first time the strange sea density is extracted independently of
the non strange sea. The analysis is then extended to nuclear targets and
the parton distributions for iron are also provided.
Authors:F.Zomer, V.Barone, C.Pascaud
Proposed speaker: F. Zomer
Contact person:Fabian Zomer (Orsay Univ.), zomer@lal.in2p3.fr
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers: V.Barone, C.Pascaud, F.Zomer, Eur. Phys. J.
C12 (2000) 243
Notes:
341. QCD-instanton induced processes in deep-inelastic scattering
Within our ongoing investigation, we have shown that deep-inelastic scattering
(DIS) at HERA offers a unique opportunity to discover QCD-instanton induced
processes. Based on instanton-perturbation theory, we were able to calculate
the rate for the DIS regime, where the generic hard scale cuts off large
size instantons, over which one has no control theoretically. The rate
turns out to be in the measurable range at HERA, and a characteristic event
signature is found: a ``fireball''-like final state with high multiplicity,
high total transverse energy and including always strange particles. Constraints
from a recent high-quality lattice simulation were exploited and translated
into a "fiducial" kinematical region for our predictions based on instanton-perturbation
theory. Now that preliminary results of first searches for instanton-induced
events from the H1 collaboration are forthcoming, the present paper includes
a careful study of known theoretical uncertainties of our predictions.
Authors:A. Ringwald and F. Schrempp
Proposed speaker: F. Schrempp
Contact person:Fridger K.W. Schrempp (Deutsches Elektronen Synchrotron
(DESY)), fridger.schrempp@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: Nucl.Phys. B507 (1997) 134; Phys. Lett. B438
(1998) 217; Phys. Lett. B459 (1999); hep-ph/9906441; hep-ph/9909338
Notes:
365. Polarized Parton Distribution Functions
Polarized parton distribution functions are determined by using world data
from the longitudinally polarized deep inelastic scattering experiments.
A new parametrization of the parton distribution functions is adopted by
taking into account the positivity and the counting rule. From the fit
to the asymmetry data A_1, the polarized distribution functions of u and
d valence quarks, sea quarks, and gluon are obtained.
Authors:Asymmetry Analysis Collaboration)
Proposed speaker: M.Miyama (or S. Kumano)
Contact person:Shunzo Kumano (Saga University), kumanos@cc.saga-u.ac.jp
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/0001046 (Phys. Rev. D in press)
Notes:
409. Top quark spin correlations at hadron colliders at hadron colliders
correlations at hadron colliders
Future hadron collider experiments are expected to record large to huge
samples of $t\bar t$ events. The analysis of these data with respect to
$t\bar t$ spin-spin correlations requires precise predictions of the production
of these quark pairs in a general spin configuration. We report on our
computation, at next-to-leading order (NLO) in the QCD coupling, of the
spin density matrices describing $t\bar t$ production by quark antiquark
annihilation, which is the dominant production process at the Tevatron.
The strength of the $t\bar t$ spin correlation at NLO, using various spin
quantization axes will be discussed. Moreover, a brief outline of the use
of these spin correltions in the search for new phenomena will be given.
Authors:W. Bernreuther, A. Brandenburg, Z.G. Si
Proposed speaker: W. Bernreuther
Contact person:Werner Bernreuther (RWTH Aachen), breuther@physik.rwth-aachen.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-03 Heavy Flavor Physics ( Charm, Bottom, Top and Tau )
Supporting papers: hep-ph/0004184, hep-ph/9812387
Notes:
422. QCD Calculations by Numerical Integration
Calculations of observables in quantum chromodynamics at next-to-leading
order are typically performed using a method that combines numerical integrations
over the momenta of final state particles with analytical integrations
over the momenta of virtual particles. I describe the most important steps
of a method for performing all of the integrations numerically. This method
has been implemented in code for infrared-safe three jet observables in
electron-positron annihilation and I show comparisons to results using
the standard numerical-analytical method. I comment on areas where the
flexibility inherent in the completely numerical method may lead to advances
in the computational state-of-the-art.
Authors:Davison E. Soper
Proposed speaker: Davison E. Soper
Contact person:Davison E. Soper (University of Oregon), soper@bovine.uoregon.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/9910292
Notes:I am currently actively developing this method. I would
use the figures from hep-ph/9910292 to illustrate the method and then say
something about current and future developments.
444. Structure functions for a spin-one hadron and polarized antiquark
distributions
Spin structure of the proton has been investigated in detail; however,
there are few studies on polarized spin-1 hadron (e.g. deuteron) reactions
in connection with spin-dependent structure functions. We would like to
shed light on new structure functions which do not exist in the proton,
for example, by the polarized proton-deuteron Drell-Yan process. This process
has an advantage over lepton reactions in the sense that the antiquark
tensor polarization could be extracted rather easily. Furthermore, it should
be useful for finding antiquark flavor asymmetry in longitudinally-polarized
and transversity distributions.
Authors:S. Kumano
Proposed speaker: S. Kumano
Contact person:Shunzo Kumano (Saga University), kumanos@cc.saga-u.ac.jp
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: F. E. Close and S. Kumano, Phys. Rev. D42
(1990) 2377. S. Kumano, Phys. Rep. 303 (1998) 183. S. Hino and S. Kumano,
Phys. Rev. D59 (1999) 094026; D60 (1999) 054018. S. Kumano and M. Miyama,
Phys. Lett. B497 (2000) 149.
Notes:
461. Measurement of the Differential Production Cross Section of W Bosons
as a function of Transverse Momentum at sqrt(s)= 1.8 TeV
We present a measurement of the transverse momentum distribution of W bosons
produced in proton-antiproton collisions at sqrt(s)=1.8 TeV. The data were
collected by the DZero experiment at the Fermilab Tevatron Collider during
the 1994-1995 run, and correspond to 85.0 pb**-1. Based on a combined perturbative
QCD and soft-gluon resummation calculation, we find good agreement between
our results and theoretical predictions over the measured range of transverse
momentum (0-200 GeV/c).
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
462. Measurement of the Angular Distribution of Electrons from W to e nu
Decays in pbar p Collisions at sqrt(s)= 1.8 TeV
We present a preliminary measurement of the alpha_2 parameter in W to e
nu decays using data collected by the DZero detector during the 1994-1995
Tevatron run. We compare our results with next-to-leading order perturbative
QCD, which predicts an angular distribution of (1 +/- alpha_1 cos theta*+
alpha_2 cos^2theta*), where theta* is the angle between the charged lepton
and the antiproton in the Collins-Soper frame. In the presence of QCD corrections,
the parameters alpha_1 and alpha_2 become functions of p_T(W), the transverse
momentum of the W. We present the first measurement of alpha_2 as a function
of p_T(W). This measurement provides a test of next-to-leading order QCD
corrections, which have a non-negligible impact on the measurement of the
W mass.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
463. Inclusive Jet Cross Section using the kT Algorithm
DZero has previously measured the central inclusive jet cross section at
sqrt(s)=1.8 TeV using the fixed-cone algorithm. The kT jet algorithm, based
on a successive combination of jets, has recently been implemented at DZero.
A preliminary measurement of the inclusive jet cross section at sqrt(s)=1.8
TeV using the kT algorithm, will be presented.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
464. Probing BFKL Dynamics in the Dijet Cross Section at Large Rapidity
Intervals in pbar p Collisions at sqrt(s)=1800 and 630 GeV
Inclusive dijet production for large pseudorapidity intervals (delta_eta)
between the two jets has been suggested as a regime for observing BFKL
dynamics. We have measured the dijet cross section for large delta_eta
in pbar p collisions at sqrt(s)=1800 and 630 GeV using the DZero detector.
The partonic cross section increases strongly with the size of delta_eta.
The observed growth is even stronger than expected on the basis of BFKL
resummation in the leading logarithmic approximation. The growth of the
partonic cross section can be accommodated with an effective BFKL intercept
of alpha_BFKL(20 GeV)=1.65+/-0.07.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
465. Rapidity Dependence of Inclusive Jet Cross Section in pbar p Collisions
at sqrt(s)=1.8 TeV
We report on a new measurement of the rapidity dependence of the inclusive
jet production cross section in pbar p collisions at sqrt(s)=1.8 TeV using
92 pb**-1 of data collected by the DZero detector at the Fermilab Tevatron
collider. The differential cross section d^2sigma/dEt deta, is presented
as a function of jet transverse energy (ET) in five pseudorapidity (eta)
intervals, up to |eta|=3, thereby significantly extending previous CDF
and DZero measurements beyond |eta|=0.7. The results are compared to next-to-leading
order QCD predictions. The extended range of the measurement promises to
provide greater discrimination among different parton distribution functions.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
466. The Ratio of Dimensionless Jet Cross Sections at sqrt(s)=630 GeV and
1800 GeV
The DZero collaboration has measured the inclusive jet cross section in
pbar p collisions at sqrt(s)=630 GeV. The data for pseudorapidities less
than 0.5 are combined with data previously collected at sqrt(s)=1800 GeV
to form a dimensionless ratio with smaller uncertainties. Although next-to-leading
order predictions exhibit only modest agreement with the 630 GeV cross
section, agreement is more satisfactory with the ratio. In particular,
for most parton distribution functions, the dependence on transverse momentum
is acceptable, but the absolute value disagrees with data by 10 to 15%.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
467. Ratios of Multijet Cross Sections in pbar p Collisions at sqrt(s)=1.8
TeV
We report a study of the ratio of inclusive three-jet to two-jet production
cross sections as a function of total transverse energy, in pbar p collisions
at sqrt(s)=1.8 TeV, for data collected with the DZero detector during the
1992-1993 run of the Fermilab Tevatron Collider. The measurements are well
described by next-to-leading order QCD calculations, and can be used to
gauge the sensitivity of the calculation to renormalization scales used
in modeling soft-jet emission.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
470. Subjet Multiplicities Based on a kT Jet Algorithm
Using the DZero detector, we measure the subjet multiplicity M in jets
reconstructed with a successive-combination type of jet algorithm (kT).
We select jets with 55<ET<100 GeV and |eta|<0.5, and compare similar
samples of jets at sqrt(s)=1800 and 630 GeV. The HERWIG Monte Carlo simulation
predicts that 59% of the jets are gluon jets at sqrt(s)=1800 GeV, and 33%
at sqrt(s)=630 GeV. Using this information from HERWIG, we extract the
subjet multiplicity in quark (Mq) and gluon (Mg) jets, and find the ratio
R=<Mg-1>/<Mq-1>=1.91.
Authors:The DZero Collaboration
Proposed speaker: To be decided by DZero
Contact person:Bernard G. Pope (Michigan State University),
pope@pa.msu.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:
487. Recent Structure Functions results from neutrino scattering at Fermilab
We report on the extraction of the structure functions F2, Delta xF3 =
xF3(nu)-xF3(nubar), and R(longitudinal) from CCFR neutrino-nucleon differential
cross sections. The extraction is performed in a physics model independent
(PMI) way for the first time. This first measurement for Delta xF3 is very
useful in testing models of heavy charm production. The F2 (PMI) values
measured in the CCFR neutrino experiment are now in good agreement with
the F2 (NMC) measured in muon scattering above Q2=1, thus resolving the
long-standing discrepancy between the two sets of data. Comparison of the
two sets of data below Q2=1, which provides information on the axial vector
contribution is also presented. The CCFR values for (R=sigma_L/sigma_T)
are in good agreement with muon and electron data for x>0.1. For x<0.1,
R for neutrinos is somewhat larger than R from muon and electron scattering,
as expected from the difference in charm production contributions. We also
report on an inverstigation of R in neutrino scattering for possible anomalous
large nuclear effects (at low x and Q2<1)) of the type recently reported
by the HERMES collaboration in electron scattering.
Authors:Un-Ki Yang at al (CCFR-NuTeV Collaboration)
Proposed speaker: Un-ki Yang
Contact person:Un-ki YANG (Univ. of Chicago), ukyang@hep.uchicago.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:We plan to submit two papers to PRL within 3 weeks.
489. SCREENING CORRECTIONS IN HARD DIS CHANNELS IN THE SMALL $Q^2$ AND
x LIMITS
In as much as it is obvious that s-channel unitarity should be manifested
in hard DIS reactions, it is not clear what are the kinematical scales
at which unitarity saturation effects, such as screening corrections (SC),
become important. While the DIS $\gamma^*p$ total cross section, or $F_2$,
data are well reproduced by the DGLAP evolution with no SC signatures,
there are compelling experimental indications by both H1 and ZEUS suggesting
deviations from DGLAP predictions in the small $Q^2$ and x limits in specific
diffractive channels. In this investigation we provide a detailed study
of $J/\Psi$ photo and DIS production which is coupled to a parallel analysis
of the $Q^2$ logarithmic slope of $F_2$. Our investigation is based on
the observation that the $J/\Psi$ cross section is proportional, in the
LLA of pQCD, to $(xG(x,Q^2))^2$. The contribution of $xG$ is dominant in
the pQCD calculation of $\partial F_2/\partial \ln Q^2$ in the small x
limit, enabling us a combined analysis. In the first phase of our investigation
we have found that none of the latest editions of input parton distribution
functions (GRV(98), MRS(99), CTEQ5) provides an adequate simultaneous description
of both channels. We then proceed to show that if we take GRV(98)NLO input
and correct it for SC, we obtain an excellent reproduction of the compiled
high energy $J/\Psi$ data. The calculation depends on one parameter, the
radius associated with the rescattering process, which is found to be $R^2=8GeV^{-2}$.
With this input we obtain, also, a good reproduction of $\partial F_2/\partial
\ln Q^2$. The SC are consistently calculated for both the percolation of
a $\bar{q}q$ through the target and the screening of the gluon parton distributions
which form the base of our calculation.
Authors:E. Ferreira, E. Gotsman, E. Levin, U. Maor, E. Naftali
Proposed speaker: Uri Maor
Contact person:Uri Maor (Tel-Aviv University), maor@post.tau.ac.il
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
561. Study of direct-photon and neutral-pion production
We present a study of direct-photon and neutral-pion production in hadronic
interactions, focussing on comparisons of the measured photon/pion ratio
with predictions from NLO pQCD. We also compare the data with a phenomenological
model that takes rough account of any additional soft-gluon emission needed
to accommodate the data. With the recently reported large corrections from
a resummation of soft-gluon contributions, a consistent picture appears
to be emerging for the origin of the deviations from predictions based
on NLO pQCD in inclusive direct-photon and neutral-pion production.
Authors:E706 et al
Proposed speaker: T. Ferbel
Contact person:Tom Ferbel (University of Rochester), ferbel@pas.rochester.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
563. Inclusive production of omega mesons at large transverse momenta in
pi-Be interactions at 515 GeV/c
We present results on the production of omega mesons at high transverse
momenta in interactions of negative pions with Be at 515 GeV/c. The data
span the kinematic range of transverse momenta between 3.5-8 GeV/c. We
compare the measured cross section with expectations from Monte Carlo QCD
generators. The relative yield of omega to neutral pions is used to extract
the ratio of vector to pseudoscalar meson production for the first generation
of quarks.
Authors:E706
Proposed speaker: T. Ferbel
Contact person:Tom Ferbel (University of Rochester), ferbel@pas.rochester.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
592. A QCD analysis of polarised parton densities
We have analysed global data on deep-inelastic polarised lepton-hadron
scattering. We find that it is possible to fit the data with strongly broken
SU(2) flavour for the polarised sea densities. This can easily be tested
in W production at polarised RHIC. The data fails to pin down polarised
singlet sea quark and gluon densities. We explore the uncertainties in
detail and show that improvement in statistics, achievable at polarised
HERA for measurement of the A_1 asymmetry at moderately low values of x,
have large payoffs in terms of the improvement in measurement of gluon
and sea quark densities.
Authors:Dilip Kumar Ghosh, Sourendu Gupta, D. Indumathi
Proposed speaker: D. Indumathi
Contact person:D. Indumathi (The Institute of Mathematical Sciences,),
indu@imsc.ernet.in
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
616. Inclusive Production of D* Mesons in Photon-Photon Collisions at sqrt(s)_ee=183
and 189 GeV and a First Measurement of F2^gamma_c
The inclusive production of charged D* mesons in photon-photon collisions
has been measured using the OPAL detector at LEP at e+e- centre-of-mass
energies of 183 and 189 GeV. For events without an observed scattered electron
(untagged), direct and single-resolved events are studied separately. Differential
cross-sections as functions of the D* transverse momentum and pseudorapidity
are presented in the kinematic region 2 GeV < pt_D* < 12 GeV and
|eta_D*| < 1.5. They are compared to next-to-leading order (NLO) perturbative
QCD calculations. The total cross-section for the process e+e- --> e+e-
c cbar where the charm quarks are produced in the collision of two quasi-real
photons is measured to be 842 +- 97(stat) +- 75(syst) +- 196 (extrapol.)
pb. Using the tagged events, the charm structure function of the photon
has been measured in the kinematic range 0.0014 < x < 0.87 and 5
GeV^2 < Q^2 < 100 GeV^2. The result is compared to an NLO perturbative
QCD calculation.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller (CERN), dave.miller@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: CERN-EP/99-157, submitted to Eur. Phys. J.
C http://opal.web.cern.ch/Opal/pubs/paper/html/pr294.html
Notes:Related to abstracts 109 and 110 submitted to session PA-02
and PL-12, Soft processes
626. QCD Studies in e+e- Annihilation at sqrt(s) from 30 GeV to 189 GeV
We present results obtained from a study of the structure of hadronic events
recorded by the L3 detector at various centre-of-mass energies. The distributions
of event shape variables and the energy dependence of their mean values
are measured from 30 GeV to 189 GeV and compared with various QCD models.
The energy dependence of the moments of event shape variables is used to
test a power law ansatz for the non-perturbative component. We obtain a
universal value of the non-perturbative parameter $\alpha_{0}$ = 0.537
+- 0.073. From a comparison with resummed O(alphaS^{2}) QCD calculations,
we determine the strong coupling constant at each of the selected energies.
The measurements demonstrate the running of alphaS as expected in QCD with
a value of $\as (mZ)$ = 0.1215 +- 0.0012 (exp) +- 0.0061 (th).
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile (CERN), Simonetta.Gentile@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:in preparation
630. Preliminary QCD results at sqrt(s) between 192 GeV and 202 GeV
We present preliminary results obtained from a study of the structure of
hadronic events recorded by the L3 detector at centre-of-mass energies
from 192 to 202 GeV. The distributions of event shape variables and the
energy dependence of their mean values are compared with various QCD models.
From a comparison with resummed O(alphaS^{2}) QCD calculations, we determine
the strong coupling constant at these energies. The charged particle multiplicity
distributions and inclusive momentum spectra are also studied from 189
to 202 GeV and the energy dependence of the peak position of the $\xi$
(= -ln x) distribution is compared with lower energy measurements and QCD
expectations.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile (CERN), Simonetta.Gentile@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:in preparation
636. Measurement of the Probability of Gluon Splitting into Charmed Quarks
in Hadronic Z Decays
We have measured the probability, Ng->cc, of a gluon splitting into a charm-quark
pair using 1.7 million hadronic Z decays collected by the L3 detector.
Two independent methods have been applied to events with a three-jet topology.
One method relies on tagging charmed hadrons by identifying a lepton in
the lowest energy jet. The other method uses a neural network based on
global event shape parameters. Combining both methods, we measure Ng->cc
= [2.45 +- 0.29 +- 0.53]%.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile (CERN), Simonetta.Gentile@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: Physics letters B Accepted CERN-EP/99-156,
02 November 1999. L3 preprint 194. Measurement of the Probability of Gluon
Splitting into Charmed Quarks in Hadronic Z Decays.
Notes:
637. Correlations Between Particles from Different Ws in e+e- ---> W+W-
events
The two-particle correlation function R(Q) has been measured in hadronic
Z decays, fully hadronic WW decays and mixed hadronic-semileptonic WW decays
using data collected by the DELPHI detector at LEP. Evidence for Bose-Einstein
correlations was observed in all three cases; the parameters lambda and
r characterizing the correlation in fully hadronic WW events are in agreement
with those in mixed hadronic-semileptonic WW events, as well a> in a sample
of Z decays in which the contribution from b-bbar pairs was depleted. Several
techniques were used to perform measurements of correlations between particles
arising from different Ws in fully hadronic WW decays. Having different
degrees of model dependence, these techniques show an excess of particle
pairs at low four-momenta difference in fully hadronic WW events, consistent
with the effect expected from Bose-Einstein correlations between identical
particles from different Ws.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
638. The Running of the Strong Coupling and a Study of Power Corrections
to Hadronic Event Shapes with the DELPHI Detector at LEP
Infrared and collinear safe event shape distributions and their meanvalues
are determined at various centre of mass energies. Radiative events from
the LEP1 data taking allow to access the energy regime from 40 to 65 GeV.
The results of last years data taking at centre of mass energies from 192
to 202 GeV are presented. A phenomenological analysis of many event shape
means and detailed tests of power correction models for both, meanvalues
and differential distributions, are presented. Using power corrections
and traditional Monte Carlo hadronisation models alpha_s is extracted in
O(alpha_s^2), NLLA and matched theory. This allows for a measurement of
the energy dependence of the strong coupling.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
639. Search for Colour Reconnection Effects in the Hadronic Decays of W
pairs with the DELPHI detector at LEP 2
Preliminary studies on colour reconnection effects in fully hadronic WW
decays are presented, based on the DELPHI data taken in 1997-1999. The
total luminosity analysed at centre of mass energies from 183 to 202 GeV
corresponds to 439 pb-1. The particle, energy flow, and other inclusive
distributions in jets associated to the same W boson and between jets from
two different W bosons are studied.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
640. More About the Multiplicity of Symmetric Three-Jet Events
The multiplicity of symmetric three jet events in electron-positron- annihilation
is measured in dependence of the event topology, with the Cambridge jet
algorithm being used. The measurement is compared to recent theoretical
predictions and the gluon contribution to the three jet multiplicity is
extracted as a measurement of the multiplicity of a gluon-gluon-system
N_gg at an adequate energy scale. N_gg is determined over a large range
of scale and found to be in good agreement with other measurements at lower
and higher scale values. The ratio of the multiplicites in gluon-gluon-events
and quark- antiquark-events is sensitive to the colour factor ratio CA/CF.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
641. Rapidity-Rank Structure of ppbar Pairs in Hadronic Z0 Decays
The rapidity-rank structure of protons-antiprotons pairs is used to analyze
the mechanism of baryon production in hadronic Z decay. The relative occurrence
of the rapidity-ordered configuration pMpbar, where M is a meson, and that
of ppbar adjacent pairs is compared. The data are found to be consistent
with predictions from a mechanism producing adjacent-rank ppbar pairs,
without requiring `string-ordered' pMpbar configurations. An upper limit
of 15% at 90% confidence level is determined for the pMpbar contribution.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
642. Charged and Identified Particles in the Hadronic Decay of W Bosons
and in e+e- --> qqbar from 130 to 200 GeV
Inclusive distributions of charged particles in hadronic W decays are experimentally
investigated using the statistics collected by the DELPHI experiment at
LEP during 1997, 1998 and 1999, at centre-of-mass energies from 183 to
around 200 GeV. The possible effects of interconnection between the hadronic
decays of two Ws are not observed. Measurements of the average multiplicity
for charged and identified particles in qqbar and WW events at centre-of-mass
energies from 130 to 200 GeV and in W decays are presented. The results
on the average multiplicity of identified particles and on the position
xi* of the maximum of the xi_p = log (2p/E_cm) distribution are compared
with predictions of JETSET and MLLA calculations.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Paper will be sent later
675. Hadronic Three Jet Production at Next-to-Leading Order
We present results of a next-to-leading order calculation of three jet
production at hadron colliders. This calculation will have many applications.
In addition to computing three-jet observables (spectra, mass distributions,
angular distributions), this calculation permits the first next-to-leading
order studies of jet and event shape variables at hadron colliders.
Authors:William B. Kilgore and Walter T. Giele
Proposed speaker: William B. Kilgore
Contact person:William B. Kilgore (Brookhaven National Laboratory),
kilgore@bnl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: William B. Kilgore and W.T. Giele, Phys. Rev.
D55 (1997) 7183.
Notes:
689. Symmetry tests in polarised Z0 decays to b bbar g
Angular asymmetries have been measured in polarized Z0 decays to b-bbar-g
collected by the SLD experiment at the SLC. A high purity b-bbar-g event
sample is selected utilizing lifetime information given by the SLD CCD
pixel vertex detector and the stable micron-size SLC beams, and the b-
and bbar-jets are identified using lifetime information and momentum-weighted
track charge. Forward-backward asymmetries are measured for two parity-violating
observables, the b-jet polar angle and the angle between the quark-gluon
and quark-electron planes, to test QCD. Two angular correlations between
the three-jet plane and the Z0 polarization are studied. The CP-even and
T-odd angular asymmetry, and the CP-odd and T-odd angular asymmetry are
sensitive to physics beyond the Standard Model. We measure the expectation
values of these quantities to be consistent with zero and set limits on
the correlations at the 5% level.
Authors:SLD Collaboration
Proposed speaker: P. N. Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
690. Improved studies of b fragmentation in Z0 decays
We present preliminary results of a new measurement of the inclusive b
quark fragmentation function in Z0 decays using a novel kinematic B hadron
energy reconstruction technique. The measurement is performed using 350,000
hadronic Z0 events recorded in the SLD experiment at SLAC between 1997
and 1998. The small and stable SLC beam spot and the CCD-based vertex detector
are used to reconstruct B-decay vertices with high efficiency and purity,
and to provide precise measurements of the kinematic quantities used in
this technique. We measure the B energy with good efficiency and resolution
over the full kinematic range. We compare the scaled energy distribution
of weakly decaying B hadrons with the predictions of several models of
b quark fragmentation, and also test several hypothesized functional forms.
We exclude many of these models and functional forms, and we present a
corrected distribution with a small and well defined model dependence.
The mean scaled energy is measured with a statistical precision of 0.003
(preliminary).
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
691. Measurement of the probability for gluon splitting into b bbar in
Z0 decays
We report a preliminary measurement of the rate of gluon splitting into
bottom quarks, g->b-bbar, in hadronic Z0 decays collected by SLD between
1996 and 1998. The analysis was performed by looking for secondary bottom
production in 4-jet events of any primary flavor. A new secondary vertex-reconstruction
technique was applied to each jet in order to identify b or bbar jets.
The upgraded SLD CCD-based vertex detector gives very high B-tagging efficiency,
especially for B hadrons of the low energies typical of this process. The
two most collinear tagged b/bbar jets were considered as a g->b-bbar candidate
and a neural network technique was used to remove backgrounds. We measured
the rate of secondary b-bbar production per hadronic event, g_(b-bbar),
with a statistical precision of 0.7x10^{-3}.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
692. A Preliminary Study of the Structure of b-bbar-g Events using Z0 Decays
The structure of three-jet b-bbar-g events has been studied using hadronic
Z0 decays recorded in the SLD experiment at SLAC. Three-jet final states
were selected and the CCD-based vertex detector was used to identify two
of the jets as b/bbar. The remaining jet in each event was tagged as a
gluon jet, and distributions of the gluon energy and polar angle with respect
to the electron beam were examined and were compared with perturbative
QCD predictions. These distributions are potentially sensitive to an anomalous
b chromomagnetic moment. We compare our data with theoretical predictions
including such a moment and discuss experimental limits.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
693. Production of Charged pi^+-, K^+- and p/pbar in Hadronic Z0 Decays
We present measurements of identified charged hadron production using the
full SLD data sample of 550,000 hadronic Z0 decays taken between 1993 and
1998. The SLD Cherenkov Ring Imaging Detector allows the identification
of clean samples of charged pions, kaons and protons over a wide momentum
range, providing precise tests of perturbative QCD calculations and of
fragmentation models. In addition to flavor-inclusive Z0 decays, and decays
into light, c and b flavors, selected using the SLD vertex detector, we
have studied gluon jets, light quark jets and heavy quark jets in tagged
3-jet events. In addition we have compared hadron and antihadron production
in light quark (rather than antiquark) jets, selected using the high SLC
electron beam polarization. Differences between hadron and antihadron production
at high momentum fraction provide precise measurements of leading particle
production and new, stringent tests of fragmentation models.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
694. First Direct Measurement of the Parity-Violating Coupling of the Z0
to the s-Quark
We have made the first direct measurement of the parity-violating coupling
of the Z0 boson to the strange quark, A_s, using 550,000 e^+e^- ->Z0->
hadrons events produced with a polarized electron beam and recorded by
the SLD experiment. Z0->s-sbar events were tagged by the absence of B or
D hadrons and the presence in each hemisphere of a high-momentum K^+- or
K^0_s. From the polar angle distributions of the strangeness-signed thrust
axis, we obtained A_s = 0.895+-0.066(stat.)+-0.063(syst.). The analyzing
power and u-ubar+d-dbar background were estimated from the data.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
695. A Study of Correlations Between Identified Charged Hadrons in Hadronic
Z0 Decays
We present a preliminary study of correlations in rapidity between pairs
of identified charged pions, kaons and protons using the entire SLD data
sample of 550,000 hadronic Z0 decays. Short range charge correlations are
observed between all combinations of these hadron species, confirming local
conservation of quantum numbers in the jet fragmentation process, and indicating
charge ordering among these three particle species. The rapidity range
of this effect is found to be independent of particle momentum. A strong
long-range correlation is observed between high-momentum K^+ and K^-, and
weaker long-range pi^+pi^, pi^+K^- and p-K^- correlations are observed
in light flavor events, providing new information on leading particle production
in u, d and s jets. The long-range correlations observed in c-cbar and
b-bbar events are markedly different and consistent with expectations based
on known decay properties of the leading heavy hadrons. In addition, the
SLC electron beam polarization is used to tag the quark hemisphere in each
event, allowing the first study of rapidities signed such that positive
rapidity is along the quark rather than antiquark direction. Distributions
of signed rapidity, and of the ordered signed rapidity difference between
pairs of particles, provide new insights into leading particle production
and new tests of fragmentation models.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
696. A Study of the Polarization of Lambda Hyperons in Hadronic Z0 Decays
We present a preliminary study of the polarization of Lambda^0 hyperons
produced in hadronic jets, along their flight direction and transverse
to the plane defined by the initial quark direction and the Lambda momentum.
We used a sample of 550,000 hadronic decays of polarized Z0 bosons collected
by the SLD experiment at the SLC. The high longitudinal electron beam polarization
allowed the determination of the quark (rather than antiquark) direction
with high purity. The Lambda^0 -> p pi^- decay mode was reconstructed,
and the transverse polarization studied as a function of its momentum and
momentum transverse to the thrust axis. An upper limit on such polarization
is presented. The predictions of fragmentation models are discussed.
Authors:SLD Collaboration
Proposed speaker: P.N.Burrows
Contact person:David R. Muller (SLAC), muller@slac.stanford.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
698. Spacelike and timelike characteristics of hadronic processes in analytic
perturbation theory
Analytic perturbation theory provides a self-consistent method of description
for both the spacelike and timelike characteristics of hadronic processes.
We consider the $R(s)$ ratio defined in the Minkowskian region and the
$D$ function defined in the Euclidean region corresponding to inclusive
$e^+e^-$ annihilation and $\tau$ decay into hadrons and demonstrate that
the analytic approach allows one to reduce theoretical uncertainties associated
with the renormalization scheme dependence of the truncated perturbative
series dramatically. We analyze effects of the quark masses and the role
of threshold singularities in the perturbative expansion. A new relativistic
Coulomb resummation factor is suggested.
Authors:K.A. Milton, I.L. Solovtsov and O.P. Solovtsova
Proposed speaker: K. A. Milton
Contact person:Kimball A Milton (University of Oklahoma), milton@mail.nhn.ou.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: Previous work on APT appears in hep-ph/0003030
(to appear in Eur. Phys. J C), Phys. Rev. D 60, 016001 (1999), and references
cited therein. New work on quark masses and Coulomb resummation will be
appearing in papers shortly.
Notes:This procedure allows a consistent treatment of timelike
and spacelike processes in QCD, and is stable with respect to higher loop
corrections and choice of renormalization scheme. New results on threshold
effects are very promising.
715. Multiplicity distributions of hadrons in gluon and quark jets
The solution of the equations for the generating functions of the multiplicity
distributions of quark and gluon jets in higher order perturbative QCD
is obtained. The results are compared to recent experimental data on the
mean multiplicities of gluon and quark jets, their ratio, higher moments,
and the slopes of multiplicities as a function of energy scale. The theoretical
predictions are generally quite successful when confronted with data.
Authors:I.M. Dremin and J.W. Gary
Proposed speaker: J. W. Gary
Contact person:J. William GARY (CERN), bill.gary@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: Physics Letters B459 (1999) 341; Physical
Review D61 (2000) 074009; eprint hep-ph/0004215
Notes:
727. E155x Measurements of the g_2^p and g_2^n Structure Functions
We report on measurements of the transverse spin structure functions for
the proton and neutron (deuteron) using deep inelastic electron scattering
on transversely polarized solid targets. Data cover the range 1 GeV^2 <
Q^2 < 20 GeV^2 and 0.02 < x < 0.9. Errors on these data are a
factor of three smaller than previous results, allowing meaningful comparison
of proposed models and sum rules.
Authors:E155x Collaboration
Proposed speaker: Stephen Trentalange
Contact person:Stephen Trentalange (University of California
at Los Angeles), trent@physics.ucla.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-12 Soft Interaction Processes ( Low Q2 : diffraction, two-photon
and spin structure )
Supporting papers:
Notes:
732. Spin Dependence of Massive Lepton Pair Production in Proton-Proton
Collisions
We show that massive lepton-pair production, the Drell-Yan process, should
be a good source of independent constraints on the polarized gluon density,
free from the experimental and theoretical complications of photon isolation
that beset studies of prompt photon production. We provide predictions
for the spin-averaged and spin-dependent differential cross sections as
a function of transverse momentum $Q_T$ at energies relevant for the Relativistic
Heavy Ion Collider (RHIC) at Brookhaven.
Authors:Edmond L. Berger, Lionel Gordon, and Michael Klasen
Proposed speaker: Edmond L. Berger
Contact person:Edmond L. Berger (Argonne National Laboratory
), berger@anl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/9909446, hep-ph/0001190
Notes:
733. Constraints on the Proton's Gluon Density from Lepton Pair Production,
the Drell-Yan Process
We discuss the transverse momentum distribution for the production of massive
lepton-pairs in hadron reactions at fixed target and collider energies
within the context of next-to-leading order perturbative quantum chromodynamics.
For values of the transverse momentum $Q_T$ greater than the pair mass
$Q$, $Q_T > Q$, we show that the differential cross section is dominated
by subprocesses initiated by incident gluons. Massive lepton-pair differential
cross sections are an advantageous source of constraints on the gluon density,
free from the experimental and theoretical complications of photon isolation
that beset studies of prompt photon production. We compare calculations
with data and provide predictions for the differential cross section as
a function of $Q_T$ in proton-antiproton reactions at center-of-mass energies
of 1.8 TeV, and in proton-nucleon reactions at fixed target and LHC energies.
Authors:Edmond L. Berger, Lionel Gordon, and Michael Klasen
Proposed speaker: Edmond L. Berger
Contact person:Edmond L. Berger (Argonne National Laboratory
), berger@anl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: Phys.Rev. D58 (1998) 074012, hep-ph/000127,
hep-ph/0003211
Notes:
787. Next-to-leading Order Hadronic Structure From Constituent Quark Structure
We calculate the partonic structure of Constituent quark in the NLO for
the first time. The structure of any hadron can be obtained thereafter
using a convolution Model. It is shown that while the constituent quark
structure is generated perturbatively and accounts for the most part of
the hadronic structure, there is a few percent contribution coming from
the nonperturbative sector. This contribution plays a key role in explaining
the SU(2) symmetry breaking of the nucleon sea and the observed violation
of Gottfried Sum Rule. These effects are calculated. Excellent agreement
with data is achieved both for proton and Pion in a wide range of kinematics
both in x=[10^-6, 1] and Q^2=[0.5, 5000] Gev^2.
Authors:Firooz Arash and Ali Naghi Khorramian
Proposed speaker: Firooz Arash
Contact person:Firooz Arash (Institute for Studies in Theoretical
Physics and Mathematics), arash@vax.ipm.ac.ir
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers: hep-ph/0003157
Notes:
794. Asymmetries in the pion-production of hyperons from Fermilab E791
Particle-antiparticle production asymmetries are presented for lambda,
cascade minus, and omega minus hyperons. The data come from 500 GeV/c pion
interactions in nuclei, and are sufficient to measure the asymmetries doubly-differential
in Feynman x and transverse momentum. Leading-particle-type effects agree
qualitatively with expectations from recombination models and their alternatives.
Authors:Fermilab E791 collaboration
Proposed speaker: Jeff Appel
Contact person:Milind V Purohit (Univ of S. Carolina), e791l@scuch8.psc.sc.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
795. Asymmetries in the production of /\_c+ baryons in 500 GeV/c pi-N interactions
(FNAL E791)
Asymmetries in the production of /\_c+ and /\_c- baryons in 500 GeV/c pion-nucleon
interactions from Fermilab E791 are presented. The asymmetries are measured
as functions of Feynman x and transverse momentum squared using a sample
of 1819 +- 62 /\_c's. A uniform asymmetry of (12.7 +- 3.4)% favoring /\_c+
is observed independent of both Feynman x in the range -0.1 to 0.6 and
transverse momentum squared to 8 (GeV/c)^2.
Authors:Fermilab E791 collaboration
Proposed speaker: Milind Purohit
Contact person:Milind V Purohit (Univ of S. Carolina), e791l@scuch8.psc.sc.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
802. Photoproduction of hard pions
We discuss photoproduction of hard, or high transverse momentum, pions.
The pions may be parts of jets or---at the highest transverse momentum---may
be kinematically isolated particles formed in short range reactions. We
show how hard pion production can be useful for determining polarized gluon
distributions and, at high x, quark distributions. Further, we study scaling
and duality in semi-exclusive processes. We show that there are be kinematic
regions where hard pion photoproduction will exhibit a scaling behavior
and that local duality can be expected in the semi-exclusive case, akin
to Bloom-Gilman duality in deep inelastic scattering.
Authors:Andrei Afanasev, Carl E. Carlson, and Christian Wahlquist
Proposed speaker: Carl E. Carlson
Contact person:Carl E Carlson (College of William and Mary),
carlson@physics.wm.edu
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers: hep-ph/0002271 Phys.Rev.D61:034014,2000 Phys.Rev.D58:054007,1998
Notes:
843. Hadron mass corrections to semi-inclusive DIS
Hadron mass effects in the DIS play important roles for moderate and low
$Q^2$. In the inclusive DIS, all target mass effects can be expressed in
terms of a target-mass-dependent scaling variable, which gives the so-called
Nachtmann moments in the moment analysis. In this work, we extend the results
to the semi-inclusive DIS in the current fragmentation region. We show
that all effects due to masses of target and produced hadrons can be summarized
by the "best" mass-dependent scaling variables for the parton distibution
and fragmentation functions.
Authors:Kazuhiro Tanaka
Proposed speaker: Kazuhiro Tanaka
Contact person:Kazuhiro Tanaka (Juntendo Univ.), tanakak@sakura.juntendo.ac.jp
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
853. Measurement of charm production in DIS via semileptonic decays
Open charm production in deep inelastic ep-scattering has been measured
via its semi-leptonic decay into electrons with the ZEUS detector at HERA
using an integrated luminosity of 34pb-1. An integrated cross section,
and differential cross sections as functions of W, x and Q^2 and of p_T
and eta of the electron, have been measured and compared to NLO predictions.
The charm contribution, F_2^ccbar, to the proton structure function has
been determined and compared with theoretical predictions and with the
previous ZEUS measurement based on D*+- production which was made in a
more restricted kinematical range.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
858. Measurement of D^*+- production and the charm contribution to F_2
in deep inelastic scattering at HERA
The production of D^*+-(2010) mesons in deep inelastic scattering has been
measured in the ZEUS detector at HERA using an integrated luminosity of
37 pb^-1. The decay channels D^*+ -> D^0 pi^+ (+c.c.), with D^0 -> K^-
pi^+ or D^0 -> \rightarrow K^- pi^- pi^+ pi^+, have been used to identify
the D mesons. The e^+p cross section for inclusive D^* production and differential
cross sections have been determined for a restricted kinematic region.
The observed cross section is extrapolated to the full kinematic region
in p_T(D^*) and eta(D^*) and the charm contribution, F_2^ccb(x,Q^2), to
the proton structure function is determined.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
888. Studies of dijet production in deep inelastic scattering
Dijet production has been measured in neutral current deep inelastic scattering
in the range $10 < Q^2 < 10000$ GeV$^2$ with the ZEUS detector at
HERA using an integrated luminosity of 40 pb^-1. Jets are identified using
the $k_T$ algorithm. The measured dijet cross sections are compared to
the predictions of next-to-leading-order perturbative QCD. Taking into
account the theoretical uncertainties, good agreement is found.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
890. Inclusive jet cross sections in neutral current DIS in the Breit frame
The inclusive jet cross section in neutral current deep inelastic positron-proton
scattering has been measured with the ZEUS detector at HERA using an integrated
luminosity of 38 pb-1. Double-differential cross sections are presented
as a function of the jet transverse momentum (P_t) and the squared four-momentum
transfer (Q^2), for 5 GeV $< p_T < $ 100 GeV and $Q^2 > 130$ GeV$^2$.
The results are compared to next-to-leading-order QCD calculations.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
891. Measurement of differential cross sections for dijet production in
neutral current DIS at high Q^2 and determination of alpha_s
Dijet production has been studied in neutral current DIS for 470 < Q^2
< 20000 GeV^2 with the ZEUS detector at HERA, using an integrated luminosity
of 38 pb^-1. Jets are found in the Breit frame using the longitudinally
invariant k_T-cluster algorithm. Dijet differential cross sections and
rates have been measured in a kinematic region where theoretical and experimental
uncertainties are small. The data are well described by NLO QCD. A QCD
fit of the dijet rate and cross section as a function of Q^2 allows both
a precise determination of the strong coupling constant and a test of its
energy-scale dependence.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
892. Multiplicity distributions in DIS at HERA
The multi-hadronic final state has been investigated in both inclusive
and diffractive neutral current deep inelastic ep scattering with the ZEUS
detector at HERA, using an integrated luminosity of 5.5 pb-1. The mean
charged multiplicity observed in the pseudorapidity region |eta_lab|<=1.75
has been measured as a function of its invariant mass, M_eff; it increases
faster with M_eff than ln(M_eff) in both inclusive and diffractive DIS.
The results are compared with hadron-hadron and e^+e^- data. The ZEUS measurements
are inconsistent with the universality of hadronisation in multiparticle
production observed in previous experiments at lower energies.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
893. Study of multiplicity moments in DIS at HERA
The charged-particle multiplicity in neutral current deep inelastic scattering
events with $Q^2$ > 400 GeV$^2$ has been studied with the ZEUS detector
at HERA, using an integrated luminosity of 38 $pb^-1$. The multiplicity
distributions have been studied in limited regions of phase space using
the normalised factorial moments measured in the current hemisphere of
the Breit frame. The factorial multiplicity moments have been measured
for the first time. The results are discussed in terms of perturbative
QCD and Monte Carlo models; substantial quantitative discrepancies have
been observed for high-Q^2 events.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
894. Measurement of the structure of virtual photons
Measurements of the structure of the virtual photon in the transition region
between quasi-real photons and those far from mass-shell have been made
with the ZEUS detector at HERA, using an integrated luminosity of 38 pb-1.
Dijet final states are identified, and differential cross sections are
presented in terms of x_gamma-obs, an estimator of the fraction of the
photon energy which takes part in the QCD subprocess. Comparison is made
to theoretical predictions.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
895. Measurement of inclusive prompt photon photoproduction at HERA
First inclusive measurements of isolated prompt photons in photoproduction
at the HERA ep collider have been made with the ZEUS detector, using an
integrated luminosity of 38.4 pb^-1. Cross sections are given as a function
of the pseudorapidity and the transverse energy (\eta^gamma, \E_t^gamma)
of the photon, for E_T^gamma > 5 GeV in the gamma p centre-of-mass energy
range 134-285 GeV. Comparisons are made with predictions from Monte Carlo
models. For forward eta^gamma (proton direction) good agreement is found,
but in the rear direction all predictions fall below the data.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
896. Measurement of the E_{T,jet}^2/Q^2 dependence of forward-jet production
at HERA
The forward-jet cross section in deep inelastic e^+p scattering has been
measured with the ZEUS detector at HERA using an integrated luminosity
of 6.36 pb^-1. The jet cross section is presented as a function of jet
transverse energy squared, E^2_{T,jet}, and Q^2 in the kinematic ranges
10^-2<E^2_{T,jet}/Q^2<10^2 and 2.5 10^-4<x<8.0 10^-2. The measured
cross section is compared to next-to-leading-order pQCD and to various
leading-order Monte Carlo models. Whereas all models agree with the measurements
at small E^2_{T,Jet}/Q^2, only one model, which includes a resolved photon
component, describes the data over the whole kinematic range.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
897. Measurement of azimuthal asymmetries in deep inelastic scattering
The distribution of the azimuthal angle for charged hadrons has been studied
in the hadronic centre-of-mass system for neutral current deep inelastic
positron-proton scattering with the ZEUS detector at HERA, using an integrated
luminosity of 38~pb$^{-1}$. Measurements of the dependence of the moments
of this distribution on the transverse momenta of the charged hadrons are
presented. Asymmetries that can be unambiguously attributed to perturbative
QCD processes have been observed for the first time.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
898. The Q^2 Dependence of dijet cross sections in gamma p Interactions
at HERA
The dependence of the photon structure on the photon virtuality, Q^2, is
studied in the reaction e^+p -> e^+ jet jet X at photon-proton centre-of-mass
energies 134 < W < 223 GeV. Events with two jets with transverse
energy E_T^{jet} > 5.5 GeV were selected in the Q^2 ranges ~ 0~GeV^2, 0.1-0.55
GeV^2, and 1.5-4.5 GeV^2. The dijet cross section as a function of the
fractional momentum of the photon participating in the hard process, x_gamma^obs,
has been compared to NLO pQCD and leading-order Monte Carlo programs; none
gives a good description of the data.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
899. High-mass dijet cross sections in photoproduction at HERA
TDijet differential cross sections for the reaction e+p -> e+ jet jet X
with quasi-real photons have been measured with the ZEUS detector at HERA
using an integrated luminosity of 42.5 pb^-1. The cross sections are given
for photon-proton centre-of-mass energies in the range 134 <W< 277
GeV and refer to jets at the hadron level using the kt-cluster algorithm.
The differential cross sections as a function of the dijet mass (M^{JJ})
and as a function of the angle between the jet-jet axis and the beam direction
in the dijet centre-of-mass system (cos(theta^*)) have been measured for
M^{JJ} above 47 GeV and |cos(theta^*)|<0.8. The dijet cross section
as a function of chi=(1+|cos(theta^*))/(1-|cos(theta^*)|) has been measured
in different M^{JJ} regions. Next-to-leading-order (NLO) QCD calculations
describe the shape of the measured cross sections well. No significant
discrepancy between data and NLO QCD calculations has been observed up
to M^{JJ} ~ 140 GeV.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
906. Substructure dependence of jet cross sections in photoproduction at
HERA
Differential cross sections for jets produced in photoproduction at centre-of-mass
energies in the range 134-277 GeV have been measured with the ZEUS detector
at HERA using an integrated luminosity of 42.5 pb^-1. Jets are identified
using the longitudinally invariant kt-cluster algorithm. Measurements of
the differential cross sections as a function of the jet pseudorapidity
and transverse energy are presented for jets characterised either by their
size or by their subjet multiplicity. Leading-logarithm parton-shower Monte
Carlo calculations of resolved- and direct-photon processes are compared
to the results and used to disentangle the contributing two-body hard-scattering
subprocesses.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
909. Measurement of event-shape variables in neutral current DIS at HERA
Event-shape variables in the current region of the Breit frame have been
measured in deep inelastic ep scattering with the ZEUS detector at HERA
using an integrated luminosity of 40 pb^-1. The variables thrust, jet broadening,
invariant mass and the C parameter have been measured over the kinematic
range 6 10^-4 < x < 0.8 and 10 < Q^2 < 40000 GeV^2. A comparison
of the mean values of these distributions as a function of mean Q with
NLO QCD predictions allows a test of the validity of the power-correction
approach.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
910. Prompt photon measurements in photoproduction at HERA
The production of prompt photons has been measured with the ZEUS detector
at HERA using an integrated luminosity of 37 pb-1. Inclusive cross sections
as a function of photon pseudorapidity and transverse energy are compared
with leading-order Monte Carlo models and with parton-level NLO QCD calculations.
A study of the intrinsic parton transverse momentum, k_T, in the proton
has been performed using the kinematical properties of events with a measured
jet as well as a prompt photon. The results are compared with earlier high-energy
proton-scattering measurements which had suggested unexpectedly high values
of parton k_T in the proton.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
916. Jet Physics in e+e-: Steps Towards NNLO
We discuss the recent progess towards the calculation of three-jet like
observables in electron-positron annihilation in next-to-next-to-leading
order of perturbative QCD. In particular, we outline new techniques for
the computation of the two-loop integrals appearing in the virtual corretions
to these observables.
Authors:Thomas Gehrmann
Proposed speaker: Thomas Gehrmann
Contact person:Thomas Gehrmann (U. Karlsruhe), Thomas.Gehrmann@phys.uni-karlsruhe.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:Please inform me about acceptance before May, 1st, since
my application for a travel grant requires acceptance of the proposed talk.
(001)
926. NLO Analysis of Inclusive and Semi-Inclusive Polarized DIS data
We perform a combined next to leading order analysis of both inclusive
and semi-inclusive polarized deep inelastic scattering data, paying particular
attention to the impact of semi-inclusive data in the extrac tion of the
sea quark and gluon spin dependent densities.
Authors:D. de Florian, R. Sassot
Proposed speaker: Rodolfo Sassot
Contact person:Rodolfo - Sassot (FCEyN Universidad de Buenos
Aires), sassot@df.uba.ar
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (022)
943. Measurement of Radiative Deep Inelastic Scattering with the H1 Detector
at HERA
The cross section of radiative neutral current deep inelastic positron-proton
scattering, where a photon is emitted in the direction of the incoming
positron, is measured in the kinematic range 0.5 < Q^2 < 15 GeV^2
and 10^-5 < x < 10^-3. The data was recorded in 1997 and corresponds
to an integrated luminosity of 15 pb^-1. The variation of the incoming
positron energy due to initial state radiation is used to access the longitudinal
structure function F L(x,Q^2).
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (042) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #946.
945. Measurement of the Proton Structure Functions and the Gluon Momentum
Distribution at low x at HERA
A high statistics measurement of the inclusive deep-inelastic positron-proton
scattering cross-section is reported for four-momentum transfers squared
1.5 =< Q^2 =< 150 GeV^2 and for Bjorken-x values 3 x 10^-5 =<
x =< 0.2. New H1 instrumentation in the backward region leads to substantially
improved systematic precision as compared to previous data. The range of
inelasticity y is extended towards low y ~= 0.004, into the region covered
by fixed target lepton-nucleon scattering experiments, and towards large
y up to 0.89 thereby providing a determination of the longitudinal structure
function F L(x,Q^2). A QCD analysis of the H1 deep-inelastic scattering
cross-section data allows the gluon distribution xg(x,Q^2) to be derived
with improved accuracy at low $x$. The strong interaction coupling constant
is obtained in Next-to-Leading Order in a joint determination of xg and
alpha s(M Z^2) using H1 e-p and fixed target mu-p inclusive deep inelastic
scattering cross-section data.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (044) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #944.
947. A Measurement of the Deep Inelastic Scattering Cross Section at Low
Q^2 and Bjorken x at HERA
New preliminary results are presented of the deep inelastic scattering
cross section in the Q^2 range 1 to 15 GeV^2 for inelasticities y up to
0.9. Using the cross section derivatives d sigma/d log y, improved data
are obtained on the longitudinal structure function F L(x,Q^2). The data
were taken by the H1 Collaboration at HERA with positrons of 27.6 GeV energy
and protons of 920 GeV energy in a special running period with 3.5 pb^-1
luminosity in December 1999.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (046) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #948.
949. Measurement of the Proton Structure Function F 2 at very low Q^2 with
the H1 Experiment at HERA
First results on the proton structure function F 2(x,Q^2) measured with
the VLQ (Very Low Q^2) spectrometer of the H1 experiment at HERA are presented.
The VLQ spectrometer which detects electrons at very small scattering angles
consists of two identical modules each containing a tungsten-scintillator
sandwich calorimeter and a silicon strip tracker. Based on data collected
in 1999 the proton structure function F 2(x,Q^2) is presented in the kinematic
region 0.1<Q^2<0.4 GeV^2 and 10^(-6) < x < 3*10^(-5).
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (048) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #950.
952. Search for Compositeness, Leptoquarks and Large Extra Dimensions in
eq Contact Interactions at HERA
Deep inelastic ep scattering data is used to search for eq contact interactions
at scales not directly accessible at HERA. In a combined analysis of e^+p
and e^-p data limits on new phenomena are derived. For conventional contact
interactions lower bounds are set on compositeness scales Lambda^+- at
1.5 - 6.4 TeV and on leptoquark exchange for ratios of mass/coupling of
order 1 TeV. A search for gravitational effects through the exchange of
Kaluza-Klein excitations of gravitons which propagate into large extra
dimensions results in lower limits on the effective Planck scale M S around
0.7 TeV.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (051) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #951.
971. Measurement of Neutral and Charged Current Cross-Sections in Electron-Proton
Collisions at HERA
The inclusive e^- p single and double differential cross sections for neutral
and charged current processes are measured with the H1 detector at HERA.
The cross sections are measured in the range of four-momentum transfer
squared Q^2 between 100 and 30000 Gev^2. The data were taken with the H1
detector at HERA in 1998 and 1999 with an increased centre-of-mass energy
of 320 GeV. Clear evidence for parity violating Z^0 exchange is observed
when comparing this data with recent measurements of the corresponding
inclusive neutral current and charged current e^+ p cross sections.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (070)
972. Search for QCD-Instanton Induced Events at HERA
Using deep-inelastic positron-proton data collected by the H1 experiment
at HERA, a search is made for QCD-instanton induced events. The predictions
of hadronic final state quantities from a Monte Carlo simulation of instanton
events are used to select a region of phase space in which QCD-instanton
effects would be enhanced. Measurements of transverse energy, charged particle
multiplicity and the flavour and charge composition of the events are used
as discriminating variables to look for `footprints' of QCD instanton processes.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (071)
974. Search for events with an isolated high energy lepton and missing
transverse momentum at HERA
A search is performed for events with an imbalance in transverse momentum
and with an isolated high energy lepton in e^-p and e^+p scattering data
collected in the 1998-2000 HERA runs. The analysis is motivated by the
result of a similar search performed in the 1994-97 e^+p data, where one
e^- and five muon events were found showing evidence for unseen particles
carrying transverse momentum. Three of these events have kinematic properties
atypical for the expected Standard Model background, which is dominated
by W^+- production with subsequent leptonic decays.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (073) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #976.
975. Inclusive Measurement of Deep Inelastic Scattering at high Q^2 in
Positron-Proton Collisions at HERA
The inclusive e^+ p single and double differential cross sections for neutral
and charged current processes are measured with the H1 detector using the
recent data from the 1999-2000 HERA run. The cross sections are measured
in the range of four-momentum transfer squared Q^2 between 100 and 30000
Gev^2. The data are compared to the e^+ p scattering data taken in the
1994-97 running period, where a slight excess was observed at the highest
values of Q^2.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (074)
977. Measurements of 2-Jet and 3-Jet Cross Sections at High Transverse
Momentum in Photoproduction.
The cross sections of 2 and 3-jet production at high transverse momentum,
P T, in photoproduction at HERA are presented for both e^+p and e^-p data.
The cross sections, measured as a function of P T and of the 2 and 3 jet
invariant mass up to the highest values accessible at HERA, are compared
with the expectations of next to leading order QCD.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (076)-978
979. Observation of beauty production at HERA using lifetime information
bbbar production has been observed in ep collisions at an ep centre-of-mass
energy of 300 GeV. For the first time at HERA a centrally installed silicon
vertex detector is used to identify b-hadrons by their decay length.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (078) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #982.
980. Measurement of Open Beauty Production at HERA
The recent observation of open b production in ep collisions at HERA is
reported. A b enriched event sample containing muons and jets has been
selected. The muons are detected in the range 35< theta < 130 degrees
for transverse momenta above 2 GeV. The visible cross section is measured
to be 0.176+-0.016+0.026-0.017 nb while a NLO QCD calculation results in
0.104+-0.017 nb. The cross sections for electroproduction with Q^2<1
GeV^2 and photoproduction are derived from the data and found to be sigma(ep->
e bbbar X)=7.1+-0.6+1.5-1.3 nb and sigma(gamma p-> bbbar X)=111+-10+23-20
nb at an average W gammap of 180 GeV, respectively.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/9909029 (079) 5/17/00 TK/TY-Above sessoins are
the 2nd choice. Same as #981.
983. Measurement of charged D* meson production and the charm contribution
to F 2 in deep inelastic scattering at HERA
The production cross section of charged D* mesons in deep inelastic scattering
has been measured using an integrated luminosity of 18.6 pb^-1 with the
H1 detector at the ep collider HERA. The cross section, over the kinematic
range 1 < Q^2 < 100 GeV^2, 0.05 < y < 0.7, p T(D*) > 1.5 GeV
and abs(eta(D*)) < 1.5, is presented in differential and double differential
distributions of p T(D*), eta(D*), Q^2, x Bj, W and x D*. These are compared
to next-to-leading order QCD expectations. In addition, the charm contribution
to the proton structure function, F 2^{ccbar}(x,Q^2), has been determined.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (082)-984
986. J/psi Meson Production at high Q^2 at HERA
Results for inclusive and inelastic J/psi meson production in deep inelastic
ep scattering at HERA are presented. The J/psi mesons are identified via
the leptonic decay in two electrons or two muons. Compared to previous
measurements the kinematical region is extended towards higher values of
the four momentum transfer squared Q^2 and hadronic center of mass energy
W (gamma-p). In the kinematical range of 2 < Q^2 < 100 GeV^2 and
40 < W gammap < 210 GeV differential and double differential cross
sections for inclusive and inelastic production are presented. Theoretical
predictions including color singlet and color octet contributions are compared
to the data.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (085) 5/11/00 TY-This is 2nd choice; same as 1074 for
PA-07.
988. Inelastic J/psi Photoproduction
A measurement of the inelastic photoproduction cross section of the process
e^+p -> e^+ J/psi X at HERA is presented. The J/psi meson is identified
via its muonic decay channel. Single differential cross sections in a region
of very low J/psi inelasticity z and double differential cross sections
are extracted. Theoretical predictions including color singlet and color
octet contributions are compared to the data.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (087) 5/17/00 TK/TY-Above sessoins are the 2nd choice.
Same as #989.
992. QCD Interpretation of inclusive deep inelastic scattering and jet
production data at HERA
The gluon density of the proton is determined using for the first time
measured jet cross sections in addition to the scaling violations of the
proton structure function F2(x,Q^2). The NLO QCD fit is performed in Mellin
space and uses solely H1 data in a wide kinematic range of x and Q^2. The
gluon density obtained from this fit to the combined data is found to be
consistent with the gluon density derived from scaling violations only.
The dijet data provides additional information in the region of high x
(0.01 < x < 0.1).
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (091)
994. Dijet Production in Charged and Neutral Current e^+p Interactions
at high Q^2
Jet production in charged and neutral current events in the kinematic range
of Q^2 from 640 to 25000 GeV^2 is studied in deep-inelastic scattering
at HERA. The distributions of jet polar angle, transverse energy, jet resolution,
dijet mass, and other dijet variables are determined. The measured jet
distributions in charged and neutral current scattering are described by
perturbative QCD calculations in next-to-leading order. A direct, model
independent comparison of the jet distributions in charged and neutral
current events, selected in the same kinematic range, is performed. The
jet distributions in both processes are found to be compatible thus testing
the independence of QCD dynamics of the electroweak scattering process.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (093)-993
995. Measurement of 3-jet production in deep inelastic scattering at HERA
Three-jet cross sections have been measured for the first time in deep-inelastic
e-p-scattering at HERA for photon virtualities 5 < Q^2 < 5000 GeV^2
using the inclusive k t jet algorithm in the Breit frame. The data are
presented as function of Q^2, the Bjorken scaling variable x Bj, the mean
transverse energy of the jets in the Breit frame and the jet invariant
mass M jj. Moreover, in the three-jet center of mass frame the shape of
the jet energy fractions and two angles characterising the 3-jet matrix
element have been studied. The data are compared to alpha s^2 pQCD-calculations.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (094)-998
996. Measurement of an azimuthal asymmetry in deep inelastic jet production
at HERA
Using dijet data obtained in deep inelastic scattering with the H1 detector
the quantity < cos phi > is measured, where phi is the azimuthal angle
in the Breit frame between the lepton scattering plane and the plane defined
by the two jets. Jets are defined using the k t algorithm. The result is
presented as a function of k t^2 / Q^2 and compared with leading order
Monte Carlos and next-to-leading order QCD calculations. The measured distribution
demonstrates the difference between gluon and quark induced processes.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (095)
997. A Measurement of dijet rates in deep inelastic scattering at HERA
Dijet event rates, R 2, have been measured for deep inelastic scattering
in the kinematic domain of low x Bj and low squared four momentum transfer
Q^2 with the H1 detector. R 2 is measured as a function of both x Bj and
Q^2 extending a single differential analysis recently published by H1.
This allows a more detailed study of jet production at low x Bj in a regime
where both scales, the squared four momentum transfer Q^2 and the squared
jet p t, are comparable. The data are confronted with next-to-leading order
QCD calculations including both the pointlike and non-pointlike structure
of the virtual photon.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (096)
999. Single-inclusive and Forward Jets at low Q^2 at HERA
Single-inclusive jet cross sections in deep-inelastic scattering for photon
virtualities 5 < Q^2 < 100 GeV^2 are measured in a data sample corresponding
to an integrated luminosity of 20.9 pb^-1 as a function of the jet transverse
energy E T, of the ratio E T^2 / Q^2 and of the Bjorken scaling variable
x Bj. Data are compared to next-to-leading order perturbative QCD calculations
using Q^2 and E T as renormalisation scale. None of the two choices is
able to describe the data over the full phase space region, in particular
in the forward region towards the proton remnant. Possible explanations
of this discrepancies are discussed.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (098)
1000. Measurement and QCD Analysis of Jet Cross Sections in Deep-Inelastic
Scattering
Jet Production has been studied in the Breit frame in deep-inelastic scattering
over a large range of four-momentum transfers 5 < Q^2 < 15000 GeV^2
and transverse jet energies 50 < E^2 T < 3600 GeV^2. Dijet and inclusive
jet cross sections are measured double differentially and are compared
to the predictions of perturbative QCD calculations in next-to-leading
order in the strong coupling constant. At high Q^2, QCD fits are performed
and used to determine the strong coupling constant, the gluon density in
the proton and, for the first time, simultaneously both the gluon density
and the strong coupling constant.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (099)
1001. Differential Dijet Event Rates at High Q^2 in Deep-Inelastic Scattering
at HERA
Properties of dijet events are investigated in Deep-Inelastic Scattering
in the range 150 < Q^2 < 30000 GeV^2. Cross sections as function
of dijet resolution y 2 and jet polar angles are measured using different
jet algorithms. Subsamples with different jet hardness criteria are selected.
Perturbative QCD calculations in NLO give a good description of the distributions
of all dijet variables up to the highest values of Q^2. QCD Monte Carlo
models describe the data less well. The strong coupling constant alpha
s is determined. The renormalization scale dependence of alpha s is consistent
with the QCD prediction.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (100)
1002. Search for Compositeness, Leptoquarks and Large Extra Dimensions
in eq Contact Interactions at HERA
The reaction e+p->e+X is studied with the H1 detector at Hera. The data
cover momentum transfers Q^2 between 200 GeV^2 and 30,000 GeV^2 and correspond
to an integrated luminosity of 35.6 pb^(-1). The differential cross section
dsigma/dQ^2 is compared to the Standard Model expectation for neutral current
scattering and analysed to search for bar(e)e bar(q)q contact interactions.
No evidence for new phenomena is observed. The results are used to set
limits on scales within models of electron-quark compositeness, quark form
factors and the exchange of virtual heavy leptoquarks. A search for gravitational
effects mediated through the exchange of virtual gravitons which propagate
into large extra dimensions is presented.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/0003002 (101) 5/17/00 TK/TY-Above sessoins are
the 2nd choice. Same as #1005.
1003. Measurement of Di-jet Cross-Sections in Photoproduction and Photon
Structure
The production of hard di-jet events in photoproduction at HERA is dominated
by resolved photon processes in which a parton in the photon with momentum
fraction x gamma is scattered from a parton in the proton. These processes
are sensitive to the quark and gluon content of the photon. The differential
di-jet cross-section dsigma/dlog(x gamma) is presented here, measured in
tagged photoproduction at HERA using data taken with the H1 detector, corresponding
to an integrated luminosity of 7.2 pb^(-1). Using a restricted data sample
at high transverse jet energy, E (T,jet)>6 GeV, the effective parton density
f gamma,eff(x gamma) = [q(x gamma) + bar(q)(x gamma) +9/4g(x gamma)] in
the photon in leading order QCD is measured down to x gamma=0.05 from which
the gluon density in the photon is derived.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/0003011 (102) 5/17/00 TK/TY-Above sessoins are
the 2nd choice. Same as #1004.
1006. Investigation of power corrections to event shape variables measured
in deep-inelastic scattering
Deep-inelastic ep scattering data, taken with the H1 detector at HERA,
are used to study the event shape variables thrust, jet broadening, jet
mass, C parameter and two kinds of differential two-jet rate. The data
cover a large range of the four-momentum transfer Q, which is considered
to be the relevant energy scale, between 7 GeV and 100 GeV. The Q dependences
of the mean values are compared with second order calculations of perturbative
QCD applying power law corrections proportional to 1/Q^p to account for
hadronization effects. The concept of power corrections is investigated
by fitting simultaneously a non-perturbative parameter alpha (p-1) and
the strong coupling constant alpha s
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/9912052 (105) 5/17/00 TK/TY-Above sessoins are
the 2nd choice. Same as #1009.
1008. Forward pi0-meson production at HERA
High transverse momentum pi0-mesons have been measured with the H1 detector
at HERA in deep-inelastic ep scattering events at low Bjorken-x, down to
4?10^-5. The measurement is performed in a region of small angles with
respect to the proton remnant and corresponds to central rapidity in the
centre of mass system of the virtual photon and proton, a region expected
to be particularly sensitive to QCD effects in hadronic final states. Differential
cross-sections for inclusive pi0-meson production are presented as a function
of Bjorken-x and the four-momentum transfer squared, Q**2, and as a function
of transverse momentum and pseudorapidity. A recent numerical BFKL calculation
and predictions from QCD models based on DGLAP parton evolution are compared
with the data.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/9907030 (107) 5/17/00 TK/TY-Above sessoins are
the 2nd choice. Same as #1007.
1010. Measurement of neutral and charged current cross-sections in positron-proton
collisions at large momentum transfer
The inclusive single and double differential cross-sections for neutral
and charged current processes with four-momentum transfer squared Q^2 between
150 and 30 000 GeV^2 and with Bjorken x between 0.0032 and 0.65 are measured
in e^+p collisions. The data were taken with the H1 detector at HERA between
1994 and 1997, and they correspond to an integrated luminosity of 35.6
pb^-1. The Q^2 evolution of the parton densities of the proton is tested,
yielding no significant deviation from the prediction of perturbative QCD.
The proton structure function F 2(x,Q^2) is determined. An extraction of
the u and d quark distributions at high x is presented. At high Q^2 electroweak
effects of the heavy bosons Z and W are observed and found to be consistent
with Standard Model expectation.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper (DESY), Peter.Schleper@desy.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:see hep-ex/9908059 (109)
1012. Symmetry violation of the polarized light-flavor sea-quark distrubution
For unpolarized parton distributions, the flavor symmetry of light sea-quarks
is broken as seen from the NMC, the E866/NuSea and the HERMES experiments.
But for polarized ones, is the symmetry of polarized sea-quarks of $主elta半ar
u$ and $主elta半ar d$ also violated ? It is very important for solving
"the proton spin crisis" to know if $主elta半ar u(x)$ is equal to $主elta半ar
d(x)$ or not, and further to determine their own values. Here, we estimate
the value of the difference between $主elta半ar u$ and $主elta半ar d$ from
recent data of semi--inclusive processes with longitudinal polarized lepton
beams and longitudinal polarized fixed targets measured by SMC at CERN
and HERMES at DESY.
Authors:T. Yamanishi and T. Morii
Proposed speaker: T. Yamanishi
Contact person:Teruya Yamanishi (Fukui Univ. of Tech.), yamanisi@ccmails.fukui-ut.ac.jp
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes: (111)
1034. An improved determination of the b-quark mass by DELPHI
Three- and four-jet topologies from hadronic events originated by $b$-
(massive) and $uds$- (light) quarks are studied using different observables
by the DELPHI detector at LEP. The experimental results are compared to
theoretical predictions including NLO radiative corrections with mass effects
and consequently a value of the $b$quark mass is extracted. The impact
on the measurement of the various jet clustering algorithms is annalyzed
with great detail. The systematic uncertainties of the measurement arising
from the fragmentation process including the model dependence of HERWIG
versus PYTHIA, the $b$-quark fragmentation function and the B-hadron decay
tables are studied and reduced according to our present knowledge. Using
the same annalysis the result is also interpreted as a test flavour independence
of strong coupling constant.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi (), Clara.Matteuzzi@cern.ch
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:paper will follow
1048. Measurement of the proton structure function F_2 in e^+p collisions
The proton structure function F_2 has been measured in e^+p scattering
in the range 2.5 < Q^2 < 30000 GeV^2 using an integrated luminosity
of 30~pb^{-1} with the ZEUS detector at HERA. The data were collected at
a center-of-mass energy of 300 GeV. For Q^2 < 50 GeV^2, the measurement
covers the range 5*10^{-5} < x < 0.17, providing considerable overlap
with measurements from fixed target experiments. F_2 has been extracted
from a data set 12 times larger than previously published. As a result
the uncertainty in the measurement is systematics dominated for Q^2 <
800 GeV.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
1049. Measurement of high-Q^2 neutral-current e^\+- p deep inelastic scattering
cross sections and a first measurement of the structure function xF_3 at
HERA
Neutral current deep inelastic scattering cross sections in e^-p and e^+p
scattering have been measured using the ZEUS detector at HERA. A first
measurement of the structure function xF_3 has been made by combining the
e^-p data sample of 16 pb^-1, collected at a center-of-mass energy of 318
GeV, with the e^+p sample of 30 pb^-1, collected at a center-of-mass energy
of 300 GeV.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
1050. Measurement of high-Q^2 charged-current e^+- p deep inelastic cross
sections at HERA
Charged-current deep inelastic scattering cross sections in e^-p and e^+p
scattering have been measured using the ZEUS detector at HERA. The data
were collected at a center-of-mass energy of 318 GeV and correspond to
e^- luminosities of 16 pb^{-1} and e^+ luminosities of 40 pb^{-1}. The
expectations of the Standard Model are compared with the results of the
measurements.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
1051. Measurement of the proton structure functions F_2 and F_L using events
containing initial state radiation at HERA
Neutral current deep inelastic e^+p scattering events containing a hard
photon radiated from the initial state positron have been studied with
the ZEUS detector at HERA using an integrated luminosity of 3.8 pb^{-1}.
The proton structure function F_2 has been measured using such events in
the kinematic range 0.3 < Q^2 < 40 GeV^2 and 8*10^{-6} < x <
1.8*10^{-1}. A first measurement of the proton structure function F_L has
been made using an integrated luminosity of 34 pb^{-1}. The results are
compared with the expectations of NLO QCD calculations.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
1066. The structure of the photon and the dynamics of resolved photon processes
in dijet photoproduction at HERA
Dijet photoproduction has been measured with the ZEUS detector at HERA
using an integrated luminosity of 38 pb^-1. Jets with E_T^jet > 14 GeV
are identified by means of a k_T-cluster algorithm. Differential cross
sections are presented as a function of x_gamma^obs, the fraction of the
photon's energy participating in the production of the two jets of highest
transverse energy, and cos(theta^*), the angle between the dijet and beam
axes in the dijet centre-of-mass system. Comparisons to next-to-leading
order QCD calculations show that the theory underestimates the data for
low-x_gamma^obs, indicating inadequacies in the photon structure parameterisations.
However, the shape of the cross section in cos(theta^*) is well described,
confirming the validity of the parton-parton dynamics in the QCD calculations.
Authors:ZEUS collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt (DESY), stefan.schlenstedt@ifh.de
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) / PL-11 Hard Interaction Processes ( High Q2 : DIS, Jets )
Supporting papers:
Notes:
1079. MLLA Measurements Using the CDF Detector at the Tevatron
Presented are studies of the jet fragmentation at CDF. Average multiplicities
and momentum distributions of hadrons in jets are compared to and found
to agree with the predictions of Modified Leading Log Approximation, which
assumes the perturbative nature of the jet fragmentation down to momentum
transfer scales as low as k T ~ Lambda QCD. Special attention was paid
to extraction of the ratio r of charged particle multiplicities in gluon
and quark jets, which was measured both in the context of MLLA calculations
and in a model-independent way by analyzing jet-jet and gamma-jet data.
The measurements are self-consistent and agree with the perturbative QCD
predictions.
Authors:CDF
Proposed speaker: A. Safanov
Contact person:Robert E Blair (Argonne National Lab.), reb@anl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:(elson1)
1080. Measurement of the Energy Dependence of Alpha s
The results from the CDF collaboration using data from the 1993-1995 Tevatron
Collider run are presented. The statistical uncertainties are significantly
reduced relative to the previous results and experimental systematics are
comparable with the uncertainties in the theoretical predictions. Despite
observed discrepancies with theory, which could be accommodated by modifications
of parton distribution functions, the inclusive jet cross section could
be described by perturbative Quantum Chromodynamics. The strong coupling
constant is measured from the inclusive jet cross section. This is the
first measurement which tests the running of alpha s over such a wide kinematical
range in a single experiment from 40 to 450 GeV. The results demonstrate
very good agreement with the QCD predictions.
Authors:CDF
Proposed speaker: Christina Mesropian
Contact person:Robert E Blair (Argonne National Lab.), reb@anl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:(elson2)
1081. Recent Photon Measurements by CDF at the Tevatron
Several updated measurements of inclusive and exclusive photon cross sections
are reviewed. The differences between previously reported results and updated
results are described. The cross section for sqrt(s)=630 GeV inclusive
photon production is compared to the 1800 GeV cross section and the results
contrasted with the corresponding jet cross sections. The photon plus muon
cross section measurement using the full run I dataset is described.
Authors:CDF
Proposed speaker: R. Blair
Contact person:Robert E Blair (Argonne National Lab.), reb@anl.gov
Sessions: PA-03 Hard Interactions ( High Q2 : DIS, Jet, Perturbative
QCD ) /
Supporting papers:
Notes:(elson3)
End of abstracts for PA-03 Hard Interactions ( High Q2 : DIS, Jet,
Perturbative QCD )